Smoke from the California wildfires has created hazy skies in Idaho and Montana, in some instances prompting air quality alerts. The smoke can be especially troublesome for people with breathing difficulties.

“What’s dangerous about (smoke particles) is that they get deep inside the lungs,” said Alfred Munzer, former president of the American Lung Association. “Our lungs were just not made for this kind of dirt.”

Although smoke makes the days uncomfortable for some people, scientists say it may actually do some good as it heads toward the Arctic. Smoke creates a thin layer of aerosols, or liquid and solid particles, which blocks some of the sunlight reaching the surface and temporarily lowers temperatures.

Depending on how widespread the smoke is, the cooling effect could last weeks or months, according to National Geographic.

Scientists have feared that the ice in the North Pole could melt completely this summer.

Parts of Montana are covered in a haze of smoke originating from several wildfires. Some of the smoke came from fires within the state, and from Canada. However, Tim Roark, environmental health director for Gallatin County, said, “It’s pretty clear that the bulk of everything is pulling in from Northern California.”

Idaho’s Department of Environmental Quality recently issued an air quality alert because smoke from California had settled on the state. “Any time you really try to breathe in heavy there’s a little pain in the lungs,” said Adam Grenzebach, an avid biker.

If smoke clouds from fires are hot enough and rise high enough into the air, they can travel substantial distances. In 2002, smoke from wildfires in Colorado and Arizona was seen in New Mexico, Nebraska and the Dakotas. Fires in Quebec spread smoke from Maine to North Carolina, and even over toward Ohio. Douglas Westphal, a meteorologist at the Naval Research Laboratory in Monterey, Calif., said smoke there had even been instances of smoke drifting from British Columbia to the Northeast, and from South America to Africa.

People with cardiac and respiratory conditions should be especially careful when wildfire smoke is present where they live. Limit time spent outdoors and physical activities, and keep a supply of any prescribed medications on hand. Dust masks generally aren’t effective in protecting from the worst pollutants caused by smoke, according to Lake County News. However, for people who need to enter a burned area to check property or clean up after a fire, these simpler masks are useful for filtering large particles.

In the summer of 2004, wildfires spread through Alaska and Canada. Scientists analyzed how the fires affected the amount of sun able to reach the Earth’s surface. The smoke over Barrow, Alaska, was so thick that its “absorption and scattering of the sun’s energy rose a hundredfold” and helped cool the region, according to National Geographic. But the smoke isn’t entirely beneficial. If smoke particles settle on snow or ice, they darken the ground, allowing the surface to absorb more heat and warm faster later on.